The present invention relates to a method for production of graft copolymers using radiations such as ultraviolet ray, electron beam, and .gamma.-rays; a pattern replication method which uses the method for production of graft copolymers; and a base polymer and a resist for graft copolymerization.
Production of graft copolymers and block copolymers (hereinafter these are referred to as "graft copolymers") by radiation induced graft copolymerization was discussed in (1) "Journal of Polymer Science", vol. 34, 1959, pages 419-438, (2) "Polymer Engineering and Science", November, 1980, vol. 20, No. 16, pages 1069-1072 and (3) U.S. Pat. No. 4,195,108.
Radiation induced graft copolymerization is to polymerize a monomer using radicals generated by irradiating a base polymer with radiation as an initiation point of reaction. This method makes it possible to produce copolymers comprising two different molecular units which cannot be produced by conventional method. However, as mentioned in the above literature (1), this method has the problem that radicals of the base polymer recombine with oxygen in the air to lose the function as initiation point of polymerization. That is, radicals are quenched and so production efficiency of copolymer which is a reaction product greatly decreases by oxygen in the air.
When graft copolymerization reaction is utilized according to the above conventional technique, it is preferred to carry out, in vacuo, all of the steps from irradiation of radiation to supply of monomer to be graft polymerized, taking into consideration the quenching of radicals of the base polymer. On the other hand, irradiation chamber and graft copolymerization chamber must be integrated and thus construction of apparatus is severely limited. If it becomes possible to once expose the steps to the air, these chambers can be separated and the graft polymerization reaction can be sufficiently induced by conventional apparatuses. Especially, separation of these chambers is desired for resist pattern fabrication process with graft polymerization which is one step in production of large scale integrated circuit. The above-mentioned conventional techniques gave no consideration in this respect.